"ABB is a collection of top-quality businesses whose performance has been hindered for many years by the company's conglomerate structure. The potential is 35 Swiss francs per share in today's terms," Cevian said in a statement. "The board has decided to keep the conglomerate structure. We think this is an unfortunate decision. The board and management team will be held accountable for realizing 35 francs."

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Activist investor Cevian Capital, which holds a 6.2 percent stake in ABB, had wanted Power Grids to be spun off into a separate company.